test(lib): fix unused warnings in doc tests

src/client/mod.rs

@@ -50,16 +50,17 @@ impl Client<HttpConnector> {
     /// # Example
     ///
     /// ```no_run
-    /// extern crate hyper;
-    /// extern crate tokio_core;
+    /// # extern crate hyper;
+    /// # extern crate tokio_core;
     ///
-    /// fn main() {
-    /// let mut core = tokio_core::reactor::Core::new().unwrap();
-    /// let handle = core.handle();
+    /// # fn main() {
+    /// # let core = tokio_core::reactor::Core::new().unwrap();
+    /// # let handle = core.handle();
     /// let client = hyper::Client::configure()
     ///     .keep_alive(true)
     ///     .build(&handle);
-    /// }
+    /// # drop(client);
+    /// # }
     /// ```
     #[inline]
     pub fn configure() -> Config<UseDefaultConnector> {

src/header/mod.rs

@@ -399,7 +399,8 @@ impl Headers {
     /// # use hyper::header::Headers;
     /// # use hyper::header::ContentType;
     /// # let mut headers = Headers::new();
-    /// let has_type = headers.has::<ContentType>();
+    /// headers.set(ContentType::json());
+    /// assert!(headers.has::<ContentType>());
     /// ```
     pub fn has<H: Header>(&self) -> bool {
         self.data.contains_key(&HeaderName(UniCase(Cow::Borrowed(header_name::<H>()))))